Thermostat for fire alarm systems



NW 3 @936 F. J. @Mmm fmy@ THERMOSTAT FOR FIRE ALARM SYSTEMS Filed 'ah 8, 1935 Patented Nov. 3, 1936 aosacss PATENT OFFICE THERMOSTAT Eon FIRE ALARM SYSTEMS l Frank J. Gilbane, St. Louis, Mo., assignor to Auto-A matic Fire Alarm System, Inc., St. Louis, Mo.,

' a corporation o! Missouri v vApplication Marchi, 1935, Serial No. 9,833

l12 claims. (c1. zoo-13s) This invention relates to thermostats particularly adapted yfor automatic iire alarm systems.

An object of this invention is to produce a thermostat switch for an automatic fire alarm system that is practical to pack and ship, install and maintain; that will withstand for reasonable periods of time the deteriorating eiects of wear and tear and ordinary corrosion and loading;

that will have parts vwhich will lwithstand al1 .0 stresses to which they are likely to be subjected under normal conditions of service; and that is y sumciently sensitive and reliable in operation.

Other and specific objects will be apparent from the following detail description taken in l5 connection with the accompanying drawing;

Fig. l is a diagram showing a device embody- .ing the invention in the environment in which it is adapted to be used;

Fig. 2 is a plan view of a thermostat switch embodying the invention, with the cover por shield in section; Fig. 3 is a vertical section; and Fig. 4 is a bottom plan view. In the specii'lc embodiment illustrated in the drawing, the base I, of molded material such as Bakelite, supports in cooperative relationship a bimetallic member 2 and a bimetallic member 3, each having an inwardly turned point adapted to engage the other member in order to make electric contact and thus close a circuit having branches connected respectively to such bimetallic members. The member 3 is positionedbelow the member 2 and is looped upon itse1f in'fs'uch a" manner that its lpoint 4 wil1 make a scratching contact with the underside of the member 2. The base I has abed 5to which thebimetallic members `2 and 3 are attached and 'has downwardlyextended feet or lugs 6 adapted to con-` tact the surfaceV to which the device is secured. thus elevating the bed 5 vabovey the surface and permitting currents of air lto passtherebeneath. A perforate casing or cage 1 coversthe bimetallic members 2 and 3,' isfattached to the base I `by inwardly turned flanges' 8 and' has attaching flanges 9 by which the device may be secured in The foregoing is a summary description of the specific embodmentillustrated inthe accompanying drawing whilev the essential features of thefinvention are pointed out lin the appended claims. The following detailed description of the inventiomand of thespeciiic embodiment illus-k' trated, will assist in understanding and practic-` ing the invention. o

The base I is preferably of a molded phenolic composition and more particularly that which is known in the trade as wood ller Bakelite, which will withstand abnormally high temperatures, such as 300 F. over an indefinite period.

The base I `has a channel I0 extending from 5 the top of a table 5a. inwardly along the bottom of the bed to accommodate a straight conductor barII, having a. terminal I2 at its outer end and a pin I3 at its inner end. The pin I3 projects through a lug I4 extending upwardly l0 from the bed 5 and forms an attaching member .for the bimetallic element 2. A channel I5 is formed similarly to the channel I0 to accommodate a conductor bar I6 having a terminal I1 at its outer end and secured by a pin I8 through 15 the bed 5 to the bimetallic member '3.

The channels I0 and I5, after the insertion of the bars II and I6 respectively', are 'lled by a wax or plastic non-conductive material. A material knownfin the trade as Leverite, which has 20 a melting point of approximately 560 F. has been found satisfactory for this purpose.

The bimetallic member 2 is secured by, the pin I3 on top of the lug or pedestal I4 and'extends substantially parallel to the bed 3 terminating 25 at its freeend in a downwardly extending point I9. The bimetallic, member 3 is secured to the bed 5 by the pin I8 directly below the member 2. The bimetallic member 3Iis in line with the memy ber 2, so that the point 'tof the member 3 will 30 contact the body of the member 2 and the point I9 of the member 2 will contact the upperloop portion of the member 3. y

It is to be understood that the bimetallic members 2 and 3 are each constructedof two layers 35 o f metal, one having a higher coe'flicientof thermal expansionl than the other. The arrangement is suchthat under heat the members will bend, the point I9 moving downwardly and they point!! moving upwardly. Under usual conditions land 40 where the thermostat is used in a circuit for a fire alarm theelements 2 and 3 are so constructed, positioned and arranged as to close'at atemperature of F. although, of course, this can be varied in laccordance with conditions. For in- 45 stance, in a boiler room or drying room it may be necessary or desirablevtojadjust the device s0 that it will close at a higher temperature.l

fThe particular shape and arrangement of the thermostat-element 3 whereby it is looped upon 50- itself'with the cooperating bar 2 'of substantially fiat contour is responsible for an important functioninwhich the point 4 will make a scraping contact. In actual practice, and as specifically illustrated. when lthe bar 2`is 2%. inches in length 55 the point 4 will scratch as much as Va of an inch along the surface of the bar 2. It is to be understood that the thermostat is intended for conditions where the bars may become coated from dust. dirt and corrosion without any attention or care over a long period of time. The scraping or scratching contact referred to is, therefore. a very important function in this environment. The arrangement of the two thermostat bars permits this scraping contact and also provides two contacts, either one of which is effective to close the circuit in which the thermostat elements are connected.

I'he casing or cage 'I is constructed of sheet metal and has bowed top and side walls, as specincally illustrated. and downwardly extending end walls identified on the drawing as 20. The edges of the end walls engage in grooves formed in the upper surface of lugs 2i extending upwardly and integral with the base I. The anges I, integral with the side walls, are turned inwardly and upwardly to engage in grooves 22 in the bottom surface of the base I.

While the molded phenolic member I is tough. yet in `comparison with the metallic shield it is pliable. For this reason the device is attached to a surface by means of flanges 8 extending downwardly and outwardly from the side walls of the cage 1. It has been found with this arrangement that the device can stand much abuse without disabling the structure. It may be subjected to blows sufficiently to remove it from a surface to which it is attached without breaking the base l or disabling the thermostat members. r

'I'he shield 1 has perforate side, top and end walls to permit the ready circulation of air in such a manner that in case of nre heated air currents will immediately contact and heat the thermostat members.

A metallic shield 23 comprises a sheet of metal, secured by the pin I8 to the bed 5, extends along the bed and turns upwardly between the contact point I9 and the adjacent perfor-ations in the end wall 20 of the cage 1. This arrangement, together with the general arrangement of the cage and thermostat members, permits the surface upon which the device is placed to be painted by spray or brush without danger of fouling the contact surfaces of the thermostat members.

Tests have indicated that a device constructed in accordance with this invention, and particularly as specifically shown in the drawing, is wholly satisfactory and efficient for the purpose for which it is intended. It is adapted to meet the unusual conditions to which such a device is subjected. is effective to prevent `accidental closing of the contacts and is effective to close the circuit and give an alarm within seconds after the surrounding 'air has been heated to a temperature above that for which the device is set.

Fig. 1 illustrates an installation of the device in a fire alarm circuit. It will be understood, of

course, that this diagram is merely exemplary and that the thermostat here illustrated may be used in a different circuit or for different pur-.

poses. The thermostat switch is connected in series in a circuit 24 with a secondary 25 of a transformer, having a primary 26 connected to a power line 2l, which may have a comparatively high voltage. It is contemplated that the primary 28 A bell 2l may be connected in the secondary circuit 24. A circuit 29 supplied by the circuit 24 is connected to actuate a relay 30 to close a power circuit 2|. the power circuit being connected to actuate a siren 22 and to light a lamp 33.

It will be understood thatvarious changes may be made in the detalls of construction, within the scope of the appended claims, without departing from the spirit of this invention.

I claim:

1. In a thermostat switch, the combination comprising a base having a bed, a pin projecting through and above the bed, a bimetallic member having one end secured to the pin and extending longitudinally above and substantially parallel with the bed with its other end free, a second pin extending above the bed. a second bimetaliic member having one end secured to said second pin and looped over itself between said first member and the bed and having its other end free, the free end of each member being adjacent a portion of the other member whereby contact may be made by either member with the other upon deformation thereof under the infiuence of heat.

2. A thermostat switch comprising an elon gated base, a flexible contact and a cooperating flexible bimetaliic member supported by the base and extending longitudinally toward one end thereof, a perforate cage secured to the base and surrounding the contact and said member and vhaving perforations in the end thereof adjacent said members, and an imperforate shield within the cage interposed between the contact and per' forations in the end wall of the cage.

3. A'thermostat switch'comprising a baseof insulation material having a bed, lugs on the bottom of the bed, positioned and adapted to elevate the bed above a surface to which the base may be attached and permits circulation of air therebetween, a contact and a cooperating bimetaliic member supported on the top of the base. elements having their inner ends embedded in said base and connected with said members respectively for connecting branches of an electric circuit to the contact and to the bimetallic member. a cage clampingly engaging the top and bottom sides of the bed, and parts in connection with said cage for attaching the device to a support.

4. A thermostat switch comprising a base of relatively pliable material. a contact and a himetalllc member supported by the base,- a cage surrounding said members and having its ends seated upon the base, and a plurality of langes integral with the case and extending into clamping engagement with the underside of said bala and cooperating with said ends to support the base by said cage.

5. A thermostat switch comprising a base of electrically non-conductive material, a contact anda bimetaliic member 'supported by the base. a metallic cage secured to the top of the bale. a plurality of flanges integral with the cage and extending into clamping engagement with the underside of `said base to support said base by said cage, and a plurality of attaching ilangm inv connection with said cage for attachment to a support to support the device.

6. A thermostat switch comprising a base having abed and feet extending downwardly from the bed to support the bed above the surface to which the switch is attached, a contact and a bimetaliic member supported by the base. a sheet metal cage positioned over the contact and bimetallic member, flanges on the cage turned lnwardly and upwardly to engage in grooves in the bottom of the base and thereby clamp the cage to the base, and attaching flanges attached to said cage and extending downwardly and outwardly from the cage for attaching the switch to said surface.

'1. A thermostat switch comprising a base, a contact and a cooperating bimetallic member supported by the base, a metallic cage having top, side and end walls surrounding the contact and bimetallic members and positioned with its end walls engaging in grooves in the base, and ilanges integral with the side walls extending downwardly and inwardly and engaging in grooves in the bottom of the base to clamp the cage to the base.

8. A thermostat switch comprising a base having a table at each end and a bed in the center elevated above the tables, a contact and a cooper-- ating bimetallic member supported by the bed, a pair of straight conductors each extending from the top of a table inwardly in a groove along the bottom of the bed, and pins through the bed connecting the Iconductors to the contact and the bimetallic member respectively.

9. In a thermostat switch, the combination comprising a base having a bed and a table at one end of the bed below the surface of the bed, a bimetallicmember and a cooperating contact member supported on and by the bed, a straight conductor extending from the top ofthe table inwardly in a groove along the bottom of the bed, and a pin through the bed connecting the conductor toy one of said members.

10. In a thermostat switch the combination comprising a base, a substantially straight elongated bimetallic member having one end supported at the base and the other end free to bend downwardly towardthe bed under the influence of applied heat, a second bimetallic member underlying a portion of said ilrst member, having one end supported by thev base, looped upon itself between the bed and the free end of said rst member and positioned to permit the other end to make contact with the underside of said first member and to permit contact between the free end of the iirst member and the upper surface of the loop on the second member.

11. In a thermostat switch, a base composed of electrically non-conductive material, a lug extending upwardly from the base, a exible bi. metallic member having one end supported by said lug and the other end free, a metallic pin embedded in said lug and holding said member thereon, a metallic Vconductor bar having its inner end embedded in said base and connected with said pin and its outer end connected with a source of electrical energy, a second metallic conductor bar having its inner end embedded in said base and its opposite end connected with a source of electrical energy, a bi-metallic member on said base in electrical communication with said last named bar, and scratching contact points on the ends of said elements respectively for engaging said respective elements when said elements are bent toward each other by heat supplied by electrical energy.

12. A thermostat switch comprising a base composed of electrically non-conductive material having grooves in the underside thereof, bi-metallic electric contact members supported by the upper side of said base, a cage mounted on the top of said base and surrounding said members,

and a plurality of attaching ilanges integral with said cage and extending inwardly under the base and upwardly /ito said grooves and maintaining clamping engagement with said base to hold said cage thereon.

FRANK J. GILBANEL 

